CLIMATIC CONTROL OF COMMERCE
In its effect upon life and the various industries of peoples, climate
is a factor even more important than topography. Of the 53,000,000
square miles of the land surface of the earth, scarcely more than
one-half is capable of producing any great amount of food-stuffs, and
only a very small area can support a population of more than one hundred
people to each square mile.
=Climate and Habitability.=--In the main, regions that are inhabited by
human beings produce either food-stuffs or something of value that may
be exchanged for food-stuffs; and inasmuch as food and shelter are the
chief objects of human activity, regions that will not furnish them are
not habitable.
The growth and production of food-stuffs is governed even more by
conditions of climate than by those of topography. Thus the great
Russian plain is too cold to produce any great amount of food-stuffs,
and it is, therefore, sparsely peopled. The northern part of Africa and
the closed basins of North America and Asia lack the rainfall necessary
to insure productivity, and these regions are also unhabitable. The
basin of the Amazon has a rainfall too great for cereals and grasses,
and the larger part of it is unfit for habitation.
All the food-stuffs are exceedingly sensitive to climate. Rice will not
grow where swampy conditions do not prevail at least during part of the
year. Turf-grass will not live where there are repeated droughts of more
than three months' duration, and corn will not ripen in regions having
cool nights. Wheat does not produce a kernel fit for flour anywhere
except in the temperate zone; and the banana will not grow outside the
torrid zone.
The two chief factors of climate are temperature and moisture. No forms
of life can withstand a temperature constantly below the freezing-point
of water, and but few, if any, can endure a constant heat of one hundred
and twenty-five degrees, although most species can exist at temperatures
beyond these limits for a short time.
=Zones of Climate.=--The belt of earth upon which the sun's rays are
nearly or quite vertical is comparatively narrow. But the inclination of
the earth's axis and the fact that it is parallel to itself at all times
of the year create zones of climate. These differ materially in the
character of the life, forms, and the activities of the people who dwell
in them.
In the torrid zone the temperature varies but little. During the season
of rains it rarely falls to 70° F., and in the dry season it is seldom
higher than 95° F. As a result, all sorts of plants that are sensitive
to low temperatures thrive in the torrid zone. It is not a climate
suitable for heat-producing food-plants, and they are not required.
The constant heat and excessive moisture of the atmosphere in the torrid
zone is apt to produce a feeling of lassitude among the dwellers in such
regions, moreover, and great bodily activity is out of question. These
conditions seriously affect the lives of the people, and, with few
exceptions, tropical peoples are rarely noted for energy or enterprise.
Great commercial enterprises are the exception rather than the rule, and
they are usually carried on by foreigners who must live a part of the
time in cooler localities.
[Illustration: THE EFFECTS OF HIGH LATITUDE--TOO COLD TO PRODUCE
BREAD-STUFFS]
Polar regions are deficient both in the heat and light necessary for
food-stuffs. Neither the grasses nor the grains fructify. As a result,
but few herbivora can live there, and these are practically restricted
to the musk-ox and the reindeer, which subsist on mosses and lichens.
The native people are stunted in growth; their food consists mainly of
raw blubber, and they are scarcely above savagery.
The temperate zones are the regions of the great industries and
activities of human life. The larger part of the land surface of the
earth is situated in these zones; moreover, the people who dominate the
world also live in them, and their supremacy is due largely to
conditions of climate. The alternation of summer and winter causes a
struggle for existence that develops the intellectual faculties and
results in industrial supremacy.
=Effects of Altitude.=--There is a decrease of temperature of 1° F. for
about every three hundred feet of ascent. But few people live at an
altitude of more than six thousand feet above sea-level, and in many
cases they depend on other localities for the greater part of their
food-stuffs, because very few of such regions produce food-stuffs
abundantly.
The chief exceptions to this rule are found in tropical regions. The
highlands of Mexico, the plateau-regions of Bolivia and Ecuador, and the
highlands of southern Asia are habitable, but they are not densely
peopled. Because of their altitude they are relieved of the enervating
effects of tropical climate at the sea-level.
Altitude likewise affects the amount of rainfall. Most plateaus are
arid. As a rule, they are arid because of their altitude; and because of
their aridity they are deficient in their power to produce food-stuffs.
They are therefore sparsely peopled.
=Effects of Rainfall.=--Regions having considerably more than one hundred
inches of rain annually are very apt to be forest-covered, and
therefore to be deficient in food-producing plants. Such localities have
usually a sparse population, in spite of the profusion of vegetation. In
some parts of India, lands that have been left idle for a few seasons
produce such a dense jungle of wild vegetation that to reclaim them for
cultivation is wellnigh impossible.
A deficiency of rainfall is even a greater factor in restricting the
density of population than too much rain. With less than fifteen or
twenty inches a year few regions produce good crops of grains and
grasses, and as a result they are sparsely peopled. Some of the
exceptions, however, are important. If the rainfall is not quite enough
to produce a normal overflow to the sea, the soil may be very rich,
because the nutrition is not leached out and carried away.
Many small areas of this character produce enormous crops when
artificially watered, and many of them, such as Persia, parts of Asia
Minor, northern Utah, and large areas of Australia and Chile have become
regions of considerable commercial importance. The products of such
regions are apt to be unique in character and of unusual value. Thus,
the wool of Persia and Australia and the fruit of the Iberian peninsula
are important articles of commerce.
In Egypt one may see the results of irrigated lands. The area of
geographical Egypt is somewhat less than half a million square miles;
the habitable part of the country is confined to a narrow strip, which,
one or two places excepted, varies from three to six miles in width. In
other words, almost the whole population of the country is massed in the
flood-plain and delta of the Nile; the remaining part is a desert
producing practically nothing.
The water that makes these lands productive falls, not in Egypt, but in
the highlands of Abyssinia, 2,000 miles away. The September overflow of
the flood-plain is the chief factor in the irrigation of these lands,
but the area has been greatly increased by the construction of barrages
and dams at Assiut and Assuan.
In the western highland region of the United States considerable areas
already have been made productive by irrigation, and it is estimated
that about two million acres of barren land can be reclaimed by
impounding the waters of the various streams now running to waste.
The distribution of rain with respect to the season in which it falls is
quite as important as its distribution with respect to quantity. In
tropical regions the ocean winds, and therefore the rainfall, come from
the east. The eastern slopes of such regions, therefore, have a season
in which rains may be expected daily, and another in which no rain falls
for several months. In the temperate zones seasonal rains for a similar
reason are on the western coasts.
Thus on the Pacific coast of the United States the rainfall varies from
about one hundred inches in southern Alaska to about twelve in San
Diego, Cal. Practically all the rain falls between October and the
following May; very little or none falls in the interval between May and
October. As a result, ordinary turf-grass, which will not withstand long
droughts, grows in only a few localities of the Pacific slope. It is
replaced by hardier grasses whose roots, instead of forming turf, grow
very deep in the soil.
Common clover will not grow in this region unless irrigated; it is
replaced by burr-clover, a variety of the plant that will not thrive in
moist regions. Now the quality of the merino wool clip of California
depends in no slight degree upon the burr-clover and other food-products
that thrive in regions of seasonal rains; that is, a great commercial
industry exists because of this feature of rainfall, and it could not
long survive in spite of it.
[Illustration: CLIMATICALLY ADAPTED TO CULTIVATION--THE LOWLANDS
PRODUCE BREAD-STUFFS AND FRUIT; THE MOUNTAIN-SLOPES ARE GRAZING REGIONS]
The seasonal rainfall also affects other agricultural industries. The
sacked wheat-crop may be left in the field without cover or protection
until the time is convenient for shipping it. The absence of summer
rains makes possible in California what would be out of question in the
Mississippi Valley, where a rainstorm may be expected every few days.
The quality of certain fruits depends largely on the season during which
the rainfall occurs. Apples, pears, and grapes grown in regions having
dry summers have usually a very superior flavor. The raisin-making
industry of California also depends on the same condition, because, in
order to insure a good quality of the product, the bunches of grapes,
after picking, must be dried on the ground. To a certain extent this is
also true of other fruits, such as dates, figs, and prunes, which
frequently are sun-dried.
The presence of large bodies of water, which both absorb and give out
their heat very slowly, tempers the climate of the nearby land and to
that extent modifies the commerce of such districts. The grape-growing
industry of central New York is a great one and its product is famous.
Its existence depends almost wholly upon the lake-tempered climate.
Elsewhere in the State the industry is on a precarious basis, and the
product is inferior.
=Effects of Inclination of the Earth's Axis.=--The inclination and
self-parallelism of the earth's axis is undoubtedly a very important
factor in climate. Practically it more than doubles the width of the
belts of ordinary food-stuffs by lengthening the summer day in the
temperate zone. Beyond the tropics the obliquity of the sun's rays are
more than balanced by the increased length of time in which they fall.
Thus, in the latitude of St. Paul, the longest day is about fifteen and
one-half hours long; at Liverpool it is nearly seventeen hours long; a
greater number of heat units therefore are received in these latitudes
during summer than are received in equatorial regions during the
twelve-hour day. Moreover, the summer temperature is higher in these
latitudes than in the torrid zone, because the sun is shining upon them
for a greater length of time.
The result of these various influences is far-reaching. Because of the
long summer days and short nights, wheat can be cultivated to the
sixtieth parallel. Corn, which gets scarcely enough warmth and light in
the torrid zone to become a prolific crop, attains its greatest yield in
the latitude of fourteen-hour days.
These factors, it is evident, carry the grain and meat industries into
regions that otherwise would not be habitable. Because the long summer
days produce these great food-crops, commerce and its allied industries
have reached their maximum development in these regions. Human
activities are greatest in the zones bounded by the thirty-fifth and
fifty-fifth parallels, the zone that includes the greater parts of the
United States, Europe, China, Japan. They are greatest, moreover,
because of their geographical position.
QUESTIONS FOR DISCUSSION
What would be the probable effect on the food-crops of the United States
were the main body of the country moved twenty degrees north in
latitude? Which would then be the wheat-growing States, the
cotton-producing States?
Illustrate the connection between occupation and altitude above
sea-level.
What difference would it make to the corn-crop were the days and nights
always twelve hours long?
What would be requisite to make Canada a centre of silk production?
Why is not cod-fishing an industry off the east coast of Florida?
Why is the greater part of the Russian Empire destined to be sparsely
peopled?
FOR COLLATERAL REFERENCE
A rain chart of the world.
A chart of isothermal lines.